A group of octahydropyrazolo[3,4-g]quinolines are described in Kornfeld and Bach, U.S. Pat. No. 4,198,415, issued Apr. 15, 1980, and in a divisional application thereof, U.S. Pat. No. 4,230,861, issued Oct. 28, 1980. Intermediates or final products of the following structures (Ia and Ib) are disclosed therein. ##STR1## wherein R is H, C.sub.1 -C.sub.3 alkyl, allyl or benzyl, R.sup.1 is H or COOZ' and Z' is C.sub.1 -C.sub.2 alkyl or phenyl-substituted C.sub.1 -C.sub.2 alkyl.
The final products disclosed therein are useful as inhibitors of prolactin secretion and in the treatment of Parkinson's syndrome. Of particular interest are compounds wherein R.sup.1 is H and R is alkyl, preferably n-propyl.
Compounds according to structures Ia and Ib are disclosed in U.S. Pat. No. 4,198,415 as compound IX in Reaction Scheme I or as compound XV in Reaction Scheme II (where the single tautomer pictured represents both tautomers, as set forth therein). In both reaction schemes, a 6-oxodecahydroquinoline of formula II is converted to the final products Ia and Ib by the following generalized reaction scheme. ##STR2##
The reagent used to transform the 1-alkyl-6-oxodecahydroquinoline (II) to the intermediate (III) is a dimethylformamide acetal such as dimethyl formamide dimethyl acetal. Structures II and III where R and R.sup.1 have their original scope are also claimed in U.S. Pat. No. 4,230,861.
In the copending application of Titus et al., Ser. No. 439,238 filed this even day, a method is disclosed for resolving a tautomeric trans-dl-racemate represented by Ia and Ib where R' is H and R is n-propyl. Also disclosed are the pharmacological properties of one of the isomers, the trans-l or 4aR,8aR isomer, which has substantially all the prolactin inhibiting and anti-Parkinsonism activity of the racemate.
It is an object of this invention to provide an optically active intermediate for use in the preparation of 4aR,8aR-5n-propyl-4,4a,5,6,7,8,8a,9-octahydro-1H(and 2H)pyrazolo[3,4-g]quinoline.